Context. Galaxy clusters represent valuable cosmological probes using
tests that mainly rely on measurements of cluster masses and baryon fractions. X-ray
observations represent one of the main tools for uncovering these quantities.

Aims. We aim to constrain the cosmological parameters Ωm and
σ8 using the observed distribution of the both values of the
concentrations and dark mass within R200 and of the gas mass
fraction within R500.

Methods. We applied two different techniques to recover the profiles the
gas and dark mass, described according to the Navarro, Frenk & White (1997, ApJ,
490, 493) functional form, of a sample of 44 X-ray luminous galaxy clusters observed with
XMM-Newton in the redshift range 0.1−0.3. We made use of the
spatially resolved spectroscopic data and of the PSF–deconvolved surface brightness and
assumed that hydrostatic equilibrium holds between the intracluster medium and the
gravitational potential. We evaluated several systematic uncertainties that affect our
reconstruction of the X-ray masses.

Results. We measured the concentration c200,
the dark mass M200 and the gas mass fraction in all the
objects of our sample, providing the largest dataset of mass parameters for galaxy
clusters in the redshift range 0.1 − 0.3. We confirm that a tight correlation between
c200 and M200 is present and in
good agreement with the predictions from numerical simulations and previous observations.
When we consider a subsample of relaxed clusters that host a low entropy core, we measure
a flatter c − M relation with a total scatter that is
lower by 40 per cent. We conclude, however, that the slope of the
c − M relation cannot be reliably determined from the
fitting over a narrow mass range as the one considered in the present work. From the
distribution of the estimates of c200 and
M200, with associated statistical (15–25%) and systematic
(5–15%) errors, we used the predicted values from semi-analytic prescriptions calibrated
through N-body numerical runs and obtain
(at 2σ level, statistical only) for the subsample of the clusters where
the mass reconstruction has been obtained more robustly and for the subsample of the 11 more relaxed LEC
objects. With the further constraint from the gas mass fraction distribution in our
sample, we break the degeneracy in the σ8 − Ωm
plane and obtain the best-fit values σ8 ≈ 1.0 ± 0.2
(0.83 ± 0.1 when the subsample of the more relaxed objects is considered) and
Ωm = 0.26 ± 0.02.

Conclusions. Analysis of the distribution of the
c200 − M200 − fgas
values represents a mature and competitive technique in the present era of precision
cosmology, even though it needs more detailed analysis of the output of larger sets of
cosmological numerical simulations to provide definitive and robust results.

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.